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New Member

I am new here and more or less a new mustang owner from west texas. About two years ago I bought my first fox, it is a 1984 GT 350 (or at least thats what it says on side of car ). It had a 302 with edlebrock lower intake, holley 4 bbl carb, long tube headers (unknown maker), MSD 6al (or something) ignition system, flowmaster H pipe. And maybe a camshaft, it sounds real throaty like I dunno deep and gurguling unless that is just the long tube H pipe c0mbo doing it. and the rear end tag says something like 2.89 or 2.98 something close to that been a while since i looked at it. Car Really was not that fast I mean a stock new charger and me were neck and neck. so I had a small issue with car after i started to fix various things leaks and gaskets things of that nature I started to notice a hissing sound and white smoke in valve covers. a coworker came over put a presure guage to my pistons and found one was not holding pressure. He told me it was piston rings and then a little later after buying my first home with a shop in back and basic tools and a engine puller and what not, I have took my engine out and apart to have discovered some debri in valves that wasn't letting it seal nice (you live you learn). and decided im just going to put a larger motor in and forget about it. so for some time now I have studied on it. And have came to realize this is some complex stuff the more I learn the more I realize I don't know what i'm doing.
I have bought a used 351w from a car yard it is out of a 89 f-150 I have torn it apart and am about to be recieving a tax refund that I will be using to get this motor turned into something that will run. I will have $2000 to get it going PLUS whatever I get From selling off the parts I no longer will need from the 302 on ebay, Or any of you that may need them.

So im looking for advice on what can and cant be put togeather. I have been going back and forth between keeping it 351 or bumping it up using the 302 pistons and a new crank to get more displacement. What im worried about is putting it togeather with a higher compression then what it had. but not knowing what combinations will work to get it with out my pistons hitting the valves and clearance issues of that nature. If just putting these 60cc heads on would get me into a nice compression then thats all I will do looking for like 10 to 10.5-1, along with rebuilding the motor getting swap kit and all the pieces and do dads (already got that part figgured out). but how do you know if they will clear your pistons with out striking the valves? stock dished pistons or the 302 pistons with a 3.85in crank. Sorry about the life story just wanted to give you some backround on this project thanks for any and all help and will post picture of this build as I go. Again if you need anything from my 302 motor that I will not be needing your more then welcome to buy it. such as lower intake headers for aod and what not. Thanks.

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Active Member

Well if it's an original GT350, you might wanna consider the possibility of leaving it stock...just a thought, but-it's your car.

If you wanna run a 351 in it, you'll need to get different headers, and accessory brackets and such, otherwise it'll drop right in the same place. Making a 393 would be awesome and have loads of torque...as far as increasing compression, yea-stock 302 heads will definitely do that...to a point where you probably cant live without 93 or better octane gas. They'll also choke the crap out of it...look at getting something better to top of a 351 unless you want to starve it. Piston to valve clearance is something you need to plan for with your piston selection. I'm kinda confused about what you had in mind though for slugs-do you want to use stock 351 pistons with the big dish or are there small reliefs? Any time you build an engine (unless it's bone stock) it's a good idea to check p/v clearance during assembly by mocking it up with clay and measuring or using a dial indicator with checking springs...

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New Member

Hello again I do plan on using aftermarket aluminum heads off ebay from kmj performance(210cc intake/60cc chamber). about the pistons mostly I just want increased compression and was trying to decide between getting new pistons or getting new crank and using pistons from my 302. will 302 pistons hold up in a n/a setup in a 393 stroker. or would it be cheaper or just better get pistons seem to be having trouble finding some that are flat with valve reliefs that are standard bore.?

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Active Member

Everyone and their brother keeps coming on here and talking about those cheap 210cc heads. They're a copy of vic jr edelbrocks...and not a great one. They'll work, but if you want to do it right, save up the extra and get something better...unless you just can't wait. As for the slugs, depends on what kind of 302 pistons your using...stock 302 pistons will work in a 393 stroker, with the right rods. But, what kind of 302 pistons are they? Standard bore 302 pistons should not be difficult to find at all...just gotta make sure you have enough valve relief for them

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Active Member

So, it looks like you're gonna go 351 instead of 393...I don't know of any aluminum heads for less than about $1200 or so aside from the ones like you mentioned...otherwise, I'll restate what I said before..."They'll work, but if you want to do it right, save up the extra and get something better...unless you just can't wait."

...or I guess if you can't swing the extra. It'll still likely run like a scalded dog...

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New Member

Thanks for the help yeah I guess I'll stay 351 for the time bein. Since I hear the crank that they come with is pretty stout. I'll just be upgrading the pistons, for more compression from what data I have put together I'll be sitting around 10.7 - 1 will that be ok with aluminum heads and high flow water pump and 185 or do degree thermostat? Thanks again.

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Active Member

The flow numbers on all those ads should read the same, but I know from looking at the pro comp heads in the past, that different vendors would publish different numbers to make you think the PC heads were more on par with the AFR 205s...which just isn't true. I'm sure they'll work fine for your purposes, and will go a long way to keeping it from being choked up-especially at the top of the RPM band where there are basically no stock heads for windsors that can keep up.

...all that being said. Ok, staying with a 351 will still be a good setup for a fox body-I have a retired friend with a '79 Fairmont wagon with a 351...Edelbrock heads, EFI conversion, Cobra intake, long tubes, etc...the car runs 11s N/A on slicks...it moves quite well.

On compression; 10.7:1 will work OK on the street, but you'll probably want to get a larger cam to bleed off some of the cylinder pressure at lower rpms-what I mean to say is that you can get away with running a bigger cam on the street because of the compression. But, make no mistake-you'll need to run premium gas and be saavy with your tuning. You'll have to make sure your timing and mixture are very well regulated because lower rpms+higher loads+high compression can=detonation and all the things that come with it. And since you're planning to run KB hyper pistons, that makes them all the more susceptible to detonation induced damage. There's some fella on here that's dealing with the damage incurred from detonation in a 351 now...part of the piston was missing down to the top ring land...really ugly. So-just choose your components wisely...if you need some assistance, Rick91GT is a busy guy, but he builds engines for a living and I'm sure he'd probably be willing to break it down for you better than I can.

He'll ask you for your end goal and what you desire out of the car. If you're not looking for anything drastic, he might even tell you to stick with a 302 based engine...but if you really wanna go 351, I'm sure he can help you out that way too!

Oh-and the 351 crank is indeed plenty stout...I don't do much reading with 351 builds, but I can't recall ever hearing of one broken...the mains on a 351 are 3" compared to a 302's 2.25"...they can support a significantly greater bearing load due to increased swept area

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Cooling system-just get a good water pump for a factory HD truck...they usually have bigger impellers and move more water. The t-stat is only part of the equation...if your radiator can't cool the water pushed through it, a cooler t-stat won't help you one bit. So, a good radiator, water pump, and probably a 160-180* t-stat will serve you fine. I used a 180* in my supercharged combo with a 3 core brass/copper radiator, and the only time it got above 195* was in drive throughs in summer (and I live in Texas).

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New Member

I can always use a direction change if im going the wrong way wanna do it right, but have hard time explaining to wife why I need this or that much more. I started with a budget of 1200 now she bumped it up to 2000 with lots of asking. My end goal is a faster car if it runs close or around 12's in the quarter i'll be happy. I still have a day or two till my income tax is here and I make my final decission.
atm I have the 351 already and still have all my 302 stuff I have no intent on running anything but N/A. those heads are crap can you point me to any heads that are ok for my goals and maybe have ability to be ported in future. but again I can't at the moment get away with getting 1000 dollar heads. wife wants to pay bills. but if upgrading other stuff first then coming back to the heads later will work then ok. More I learn the More I realize I know nothing.

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New Member

how much power can you expect 302w stock 84 pistons to hold up to reason I ask is because I am going back and forth between changing my pistons or crank. or how much can stock 89 351w pistons hold up to. If stock cast pistons are good enough for a N/A setup maybe I can take that money and move it over to a new head selection with small chambers to still get a higher compression using the same 351w dished pistons? what do you think what would you do if under a budget, and just going N/A .

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Active Member

Stock cast pistons are stock cast pistons...the biggest problem you'll run into either way (302 or 351) would be low compression (rated @ 8.4:1 if memory serves), and you shouldn't run a power adder. I've seen people do it, but cast pistons don't hold up well to the extra heat and pressure. It's not so much the "power" level they can take so much as the heat and pressure they can handle. But, if you're only looking for 12s, a 351 with good heads, cam, intake (H/C/I) will easily accomplish your goals N/A...with cast pistons. I'm gonna toss an idea at ya, and maybe mull it over a bit; pick two of the following three words.......cheap.......fast.........reliable. Those are the two that can happen together-not all three at the same time. But, if I were trying to build an engine on the cheap and it were a 351 with some of the things you've mentioned, I'd probably do something like this for the shortblock:

Clean/inspect the stock internals
Have the assembly balanced
Zero deck the block (if your pistons are in the hole, this will help increase compression as well as square up the block)
New rings, bearings, gaskets
ARP rod bolts

Cam selection: I can't recall all the specs on the 351s, but if memory serves, they didn't cast in the taller lifter bores and provisions for a factory roller cam until '94 or '95, so you're probably gonna have to stick with a flat tappet cam-check your block, I don't want to give you bad info. Upside to that is the cams and lifters are significantly less expensive; downside is you'll want to run oil additives to keep the lobes from wearing prematurely, and you have to do the old school break-in method where you run the engine for 30 minutes between 2500-3000 rpm to work harden the lobes. Moving on-a bumpstick with about 225-235 duration at 0.050" lift (probably about .520"-.540" lift I'd guess)will make some good lopey cam noise and allow the engine to power up top pretty well.

Heads: just like Rick said-gotta choose some decent heads. Even out of the box Edelbrocks will be a huge improvement over stock...Edelbrock made over 400hp (engine dyno) with their RPM package--cam/head/intake/750 carb kit, 1 3/4 headers, and like 34* total timing. That's just an idea though...not saying you gotta go that route. You can also start looking at forums/eBay for used heads...they're all over the place. I've found used Trick Flow twisted wedges (excellent heads) used in good condition for as little as $750. Only caveat being, buyer beware...there are folks in the world that have no scruples and will bend you over.

Carb/distributor: Nothing wrong with a used carb either...many times people are upgrading and just want some kind of return on their old stuff that won't be used anymore. 700-750cfm ought to reach your goal with some tuning. Dizzy, believe it or not, the factory type duraspark distributor is up to the task...the DS II setups will throw a spark across a 0.050" gap all day long based on my past experience. That being said, the factory advance curve is kinda slow, so lighter springs in the advance mechanism would help out the midrange too. So, unless you come along a really good deal on a Mallory, MSD, Accel, or something else, a factory type dizzy will be fine, and you can save some $$. The only thing I could really recommend would be to get a better coil. An MSD/Mallory or similar multi-spark box would be a pretty good addition when you're ready to ditch the duraspark module, and I'm pretty sure Summit carries one branded under their name that operates exactly the same as the Mallory HyFire VI.

Now, what you also have to take into consideration here is the rest of the car...you may have the power to hit the times, but if you don't stiffen the chassis, and ensure the brakes are up to the task, you might have a frightful drive. The brakes on my '84 left much to be desired, so I upgraded to SN95 stuff. That's only one option of many. Lots of folks just get the better calipers from a MK VIII, correct rotors, good pads etc, the brakes will be sufficient. The rear drums...well, get the best shoes you can get and go from there.

The rear axle in your car, unless I missed my guess, is a 7.5" with a Ford trac-loc diff, and you might have slapper bars or quad shocks depending on the month of manufacture. There's no way I can put this other than truthfully, that rear end is WEAK...I spit the spider gears out of mine with a stock '84 5.0 launching on street tires. I upped to an Auburn diff later and it took a good beating for several years, but really man, start looking for a Mustang 8.8...the 7.5 won't live long behind a 351, or even a upgraded 302.

...unless someone already swapped an 8.8" in...take pictures, find out what's in the car...then give us an update...

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Active Member

I should probably just rename the "cam" portion to "valvetrain"...cuz you'll need some rockers that will fit aftermarket heads...the options here are nearly limitless...1.6 ratio, 1.7 ratio (gives you .030" extra lift at the valve), dozens of brands, types, etc...don't go dirt cheap unless it's a good used set of brand name pieces. A good timing set from Cloyes is available at many local parts stores and they aren't that expensive. If you run heads with studs and guideplates, you'll need to get hardened pushrods...available at dozens of mail order warehouses to include Summit, Jeg's, CNC Motorsports, etc...just measure the pushrod length and go from there. If you're not sure how to do this, google how to measure pushrods, or search pushrod length on here...tons of options-you could also purchase a book from Amazon about how to build small block Ford engines. If you've never built an engine before, it would be a worthwhile $15 IMHO. They go into pretty good detail about theory of operation, upgrades, assembly, "garage blueprinting", etc.

If you have other questions, people are nearly always on here, or you could probably shoot Rick an email and he could answer any questions you have...he's helping me out with proper fuel system config and turbo sizing for my 4.6 4V build right now...guy's a wealth of knowledge and has ties to plenty of expert agencies...

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New Member

I Will give update thanks. I do have the msd box and coil already on car got car for 3500 had a good bit of add ons but I do belive it is the 7.5 any fear in running it till it breaks and if I switch it will a 5 bolt wheel be mandatory only reason i ask is because car came with centerline wheels that I kinda like. Also what is zero deck the block? shaving off that extra .003 to bring it to 9.5? also the brakes and other upgrades will come in future to add support to body. just need it running to get to work so wife does not have to wake at 4:30 every morning. and anything I can do now that would be easier or mandotory with engine out. When I think i know what direction im running sometimes I just get stopped in my tracks. also how important would new cam bearings be?